Metal thread protector



Aug. ll, 1959 F.J. KENNEDY 2,398,943

METAL THREAD PROTECTOR Filed Oct. 5. 1955 1a az r4' 20 .all u fff- IN V EN TOR.

A'r'roRNE'Ys i mint. 'ran rnorncron lFrank J. Kennedy, Mount Lebanon, Pa., assigner, by mesne assignments, to H. K. Porter Company Inc., Pittsburgh, Pa., a corporation of Delaware Application October 5, '1955, Serial No. '538,606

2 Claims. (Cl. 13S-96) This invention relates to protectors for the threads of pipes, and particularly to thread protectors which are suitable for use on pipes of large size such as are used for oil Wells.

Thread protectors of the character indicated are commonly made of steel and they have annular end faces joined to side walls by a curved corner with an inside diameter somewhat greater than the outside diameter of the end of the pipe on which the thread protector is intended to be used. This provides a clearance beyond the mid portion of the side wall to facilitate the threading of the side wall to tit a pipe on which the threads are to be protected. In order to facilitate the placing of the protectors on the pipes, a flaring entrance to the protector is ordinarily provided at the end ofthe protector opposite the annular end wall.

Such thread protectors are in common use, but they are expensive to manufacture. Another disadvantage has been that unless the thread protectors are screwed on the pipe so tightly that they are difficult to remove, there is danger of the protectors coming unscrewed when the pipes are subject to vibration such as may be encountered during transportation.

It is an object of this invention to provide a thread protector construction which makes possible the manufacture of the thread protector from flat strip stock on automatic, multislide machines. This greatly reduces the cost of the protectors as compared with prior constructions which required extensive, successive forming operations on sections of seamless tubing. With the construction of this invention, all of the operations in making the protector are performed automatically on a multislide machine, except the threading. In order to avoid close manufacturing tolerances, the thread protector of this invention is threaded in a subsequent operation after it comes from the multislide machine in an otherwise completed condition.

Another object of the invention is to provide a thread protectorl with simple means for exerting a continuous friction force for preventing the connector from becoming unscrewed, and this force does not require that the connectory be screwed on the pipe so tightly that it is difficult to remove. With this invention, the force for retaining the connector on the threads continues to operate even, though the connector moves to some extent in, a direction to unscrew it from the threads. In the preferred construction, theend face of the thread protector has undulations or corrugations at widely spaced and angularlyl spaced locations around the longitudinal axis ofl the pipein position to contact with the end face of thepipe. These undulations are of resilient material which yields to set up a friction force against the end face, and the resilience of the contacting surfaces maintains Vthe friction force even though the thread protector ismnot screwed on the pipe as tightly as possible, and even though the thread protector moves some in a direction to unscrew it from the pipe.

2,898,943 Patented Aug. 11, 1959 Another object of the invention is to provide improved means for turning the thread protector on the pipe when screwing it on and when unscrewing it from the pipe. In the preferred' construction, notches are provided in the end face of the thread protector for receiving a Spanner wrench or a chisel or other tool by which the said protector can be rotated. This is of particular significance in connection with a connector made from a single, curved piece of metal because it locates the forces for turning the thread protector on the face of the protector which functions as a web through which a moment forceis transmitted to the side Wall of the thread protector with less tendency to break the seam at which the confronting end faces of the thread protector are joined together.

Other objects, features and advantages of theginvention will appear or be pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views;

Figure l is a side elevation of the threadv protector of this invention applied to the end of a pipe;V

Figure 2 is a sectional view, partly broken away, and on a substantially larger scale, showing the structure of Figure 1, the section being taken on the line 2-2 of Figure 3; and

Figure 3 is an end View of the structure shown in Figure 2..

Figure 1 showsv a thread protector 101ocated=overthe threads on the end of a pipe 11. The thread protector comprises a cap having a side wall 14 and an end wall 15 l(Figure 2). g

The side wall 14 has a forward portion 18 whichincludes a rounder corner which is the juncture ofl theside wall with the end wall 15, and the inside diameter of the vthread protector at the forward portion 18 is of larger diameter than the. outside diameter of the end of the pipe 11. At the oppositeend of the threadlprotector, there is a flared portion 20for facilitating'the entrance of the pipe 11 into the thread protector. Between the-forward portion 18 and the flared portion 20, there is a; mid portion 22- with threads on its inside surface for screwing over threads V2.4' of thepipe 11.

When the thread protectorl is constructed for use on pipes having taperedithreads, as is usually the oase, the threads on they mid portion 22 are tapered to t the; threads 240i the pipe. The purpose of the enlargedin. side diameter of the forward portion 18 is to providea,l clearance for the holder or end of the tool used for making the thread on the inside surface of the threadi protector. The outside diameter of the flared po1'tion20w is `preferably equal to the outside diameter of the yforwafrd' portion 18. This facilitates the stacking of pipes in parallel relation.

Thethread protector 10 is made of'a'single piece ofi ,materiaL .and preferably of resilient metal, such as steel.

In the manufacture of the thread protector, all of the--, shaping operations are first performed on an automatic-,- multislide machine, and the material is then benty around a longitudinal axisV to bring. the opposite ends of thev piece together along a seam 28. The confronting faces.; on opposite sides of this seam are secured together: Ing the preferred construction, they are connected bya pro-- jection y31, on one side of the seam, ttinginto a recess: 32 on the other side of the scam. The projectionand Arecess are preferably undercut such as the dovetail yjointi shown in Figure 2. This provides a strongconnection l with iiush surfaces across which the threads can befchased inthesame yway as if the protector were madeof seam-- lesstubing. Ifdesired, the seam` canbeprovidedwith:

additional strengthby spot welds 36 located beyond-the threaded area or on the outside ofthe thread protector.

There are undulations formed by corrugations 38 at.

fangularly spaced locations around the longitudinal axis of the .thread protector. These corrugations 38 are bent inwardly and they are at locations to contact with the 'end face of the pipe 11 when the thread protector is fscrewed on the pipe.

In order to obtain a substantial detiection of the corrugations 38, without requiring excessive force in screwing the thread protector on the pipe, the number of corrugations should be limited. The preferred construction includes only three corrugations 38, and these are located at approximately 120 from one another so that the force for deflecting them is evenly distributed around the pipe. To further facilitate deflection of the metal of the corrugations 38, and to have a greater amplitude of deflection without exceeding the elastic limit of the material, the corrugations 38 should be of substantial width. When the thread protector is made of steel, the corrugations 38 are partially flattened by the pressure against the end face of the pipe and this provides a. substantial friction force for preventing the thread protector from becoming unscrewed as the result of vibration. Even if the thread protector turns to some extent in a direction to unscrew it from the pipe, the pressure of the corrugations 38 against the end wall continues to maintain a friction force for preventing further rotation of the thread protector.

The end face has notches 40 for -receiving a tool Toy which the thread protector can be rotated. A Spanner wrench can be used, or a chisel, as previously explained. In the construction illustrated, the notches 40 are substantially square recesses in the inside edge of the end face '15, as best shown in Figure 3. The notches 40 are 'preferably evenly spaced around the axis of the thread protector. Different numbers of notches can be used, but if an even number are used with each notch diametrically kopposite from another notch, the construction can be used 'with simple types of wrenches.

The notches 40 can be of various shapes, but in the preferred construction at least one and preferably both of the sides of the notches 40 extend in directions substantially radial with respect to the longitudinal axis of the thread protector.

The end face 1S preferably extends, throughout most of its area, in a plane normal to the longitudinal axis of the pipe and thread protector. The location of the notches 40 in this inwardly extending end face 15, which is a flange of the thread protector, results in an application of force to the thread protector at a region and in directions which reduce the tendency of the force to break open the portion of the seam 28 along the side wall 14 of the thread protector. Any distortion of that part of the seam 28 could result in a burr along the threads of the mid portion Z2, and the provision of the notches 40 for turning the thread protector is, therefore, a protection to the threaded part of the seam 28.

The preferred construction of the invention has been illustrated and described, but changes and modifications can be made, and some features can be used in dierent combinations, without departing from the invention as defined in the claims.

What is claimed is:

1. In a thread protector of the class wherein a single piece of metal is curved to bring its opposite longitudinal edges adjacent to one another and said edges are connected to form a generally cylindrical wall for surrounding the threads to be protected and in which a liange at one end of the piece of metal curves inwardly and extends across the end face of the wall of a pipe on which the protector is used, the improvement which comprises a side wall of increased diameter toward both ends and with a throat section intermediate the ends having a multi-convolution, continuous thread formed in lthe inner surface of the wall at the throat section for screwing over the pipe threads that are to be protected, the se'am at which the opposite edge of the metal meet being a butt seam and having a ilush dovetail connection including a tab extending from one edge and engaged in a complementary groove in the opposite edge and with surfaces of the metal on opposite sides of the seam Hush with one another and with a plurality of successive convolutions of the continuous helical thread extending across the flush seam at the dovetail connection, the outside surface of the protector over the threads being smooth and free of undulations from the threads, and the end tiange merging with the side wall at a juncture where the diameter of the side wall is greater than at the throat sections, and in which the end iiange is annular and extends radially inward and has an inside diameter substantially less than the inside diameter of the pipe on which the thread protector is intended to be used, and said end -flange has undulations extending inwardly and located at widely spaced angular locations around the axis of the pipe and constituting the part of the end tiange that contacts with the end face of the pipe, the inner edge of the end iiange having notches therein, free of any obstruction longitudinally of the protector whereby a tool inserted in the notches can extend into the pipe on which the cap is screwed.

2. In a thread protector of the class wherein a single piece of metal is curved to bring its opposite longitudinal edges adjacent to one another and said edges are connected to form a generally cylindrical wall for surrounding the threads to be protected and in which a flange at one end of the piece of metal curves inwardly and extends across the end face of the wall of a pipe on which the protector is used, the improvement which comprises a side wall of increased diameter toward both ends and with a throat section intermediate the ends having a multiconvolution, continuous thread formed in the inner surface of the wall at the throat section for screwing over the pipe threads that are to be protected, the seam at which the opposite edge of the metal meet being a butt seam and the inside surface of the connector at the throat section having its threads extending across the seam, the end iiange merging with the side wall at a juncture Where the diameter of the side wall is greater than at the throat section, and the end iiange having several corrugations of short circumferential extent and with large angular spacing from one another around the annular extent of the flange, the corrugations being displaced inwardly at locations where said corrugations contact with the end face of a pipe on which the protector is screwed, whereby the corrugations prevent the remainder of the ange from touching the end face of the pipe, and the total axial pressure component of the pressure between the pipe and connector threads is concentrated in the localized areas of contact of the liange corrugations with the end face of the pipe to provide resilient pressure for resisting rotation of the connector in a direction to unscrew it from the pipe.

References Cited in the le of this patent UNITED STATES PATENTS 930,808 Smith Aug. 10, 1909 1,000,374 Cable Aug. 15, 1911 1,639,814 Shrum et al. Aug. 23, 1927 1,642,330 Brownstein Sept. 13, 1927 1,776,528 Unke Sept. 23, 1930 1,860,886 Brownstein May 31, 1932 1,963,535 Trotter June 19, 1934 1,999,818 McIntyre Apr. 30, 1935 2,231,794 Bradley et al Feb. 11, 1941 2,627,877 Phillips Feb. 10, 1953 2,632,355 Becker Mar. 24, 1953 2,632,478 'Ronfeldt Mar. 24, 1953 

